UI/WKWebView input file标签dismiss

iOS WebView 用<input type=file>标签打开系统相册会出现dismiss掉当前视图的bug，这是因为点击系统弹出的alertController时，会多次调用dismiss（不知原因）。如果WebView自己或者根视图是通过present出来的，则会被dismiss掉，而用navigation push出来的则没有问题。

解决办法

1. 不使用present方式展示WebView
2. 用自定义navigation套着WebView，然后override dismiss方法

class WebViewNavigationController: UINavigationController {
    override func dismiss(animated flag: Bool, completion: (() -> Void)? = nil) {
        // fix webview input-file dismiss-twice bug
        if let _ = self.presentedViewController {
            super.dismiss(animated: flag, completion: completion)
        }
    }
}

let webViewController
let nav = WebViewNavigationController(rootViewController: webViewController)
self.present(nav, animated: true, completion: nil)

Read more

• https://stackoverflow.com/questions/37380333/modal-view-closes-when-selecting-an-image-in-wkwebview-ios
• https://stackoverflow.com/questions/35999551/uiimagepickercontroller-view-is-not-in-the-window-hierarchy
• http://www.jianshu.com/p/284405e7313d
• http://www.infocool.net/kb/IOS/201612/247812.html